[H] sporadic slowdowns and stalls

[Veech]

What is the general culprit when a system experiences slowdowns and stalls? 
I'm running XP on a P4 3.0 system with 2G PC3200RAM.  a couple of months ago 
this thing zipped along.  Then it started going slower and slower, taking up 
to 2 minutes to finish booting up.  Now when I do a simple multi-task thing, 
such as click on IE while burning a CD in Nero, it takes up to a minute for 
the IE screen to load.  When it finally does, it's slow as molasses. 
Sometimes it freezes, and I have to hit the reset button.  I'm resetting the 
computer up to 4 or 5 times in a 3 hour session.  Can't be good.

I've run spybot and virus software, and everything is clean.  MSCONFIG has 
nothing enabled, although that didn't help boot-up time at all.  Is it time 
to reinstall XP?

I really am anxious to upgrade but I want a Core 2 Duo system with SLI and 
there aren't yet any boards available.  Don't know if I can hang on till the 
end of the year...